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为了解管桩沉桩过程中孔隙水压力的变化情况,通过对杭州萧山某工地的沉桩挤土效应进行现场监测,得出以下结论:场地中央的超孔隙水压力明显大于应力释放孔两侧相应深度处的超孔隙水压力,且应力释放孔内侧的超孔隙水压力也要大于应力释放孔外侧同一深度的超孔隙水压力;超孔隙水压力的动态变化规律绝大多数呈先增长后减少的趋势,沉桩距离较远时,超孔隙水压力整体变化呈缓慢增长趋势,而沉桩距离较近的时候,超孔隙水压力变化多呈先增长后减少趋势;本工程3～7m左右为粉土与淤泥质土的交界面,由于粉土与淤泥质土的渗透性不同,导致超孔隙水压力在3～7m左右会发生突变;PTC-500(65)管桩沉桩时,周围超孔隙水压力的变化明显要大于PTC-400(60)管桩沉桩时周围超孔隙水压力的变化。当沉桩距离小于5m的时候,超孔隙水压力变化比较明显;当沉桩距离超过5m的时候,超孔隙水压力变化逐渐减缓,趋于均速。
In order to understand the change of pore water pressure during the process of pile driving, the on-site monitoring of the pile-squeezing effect in Xiaoshan, Hangzhou, concluded that the excess pore water pressure in the center of the site is obviously larger than that on both sides of the stress releasing hole The pore water pressure at the corresponding depth and the excess pore water pressure inside the stress release hole should also be greater than the excess pore water pressure at the same depth outside the stress release hole.The vast majority of dynamic changes of excess pore water pressure first increased and then decreased When the pile sinking distance is far, the overall change of excess pore water pressure shows a slow increasing trend. When the pile sinking distance is relatively close, the change of excess pore water pressure tends to first increase and then decrease; about 3 ~ 7m of this project is As the interface between silt and silt soil, due to the different permeability of silt and silt soil, the excess pore water pressure will change suddenly in about 3 ~ 7m. When the pile of pile of PTC-500 (65) The change of pore water pressure is obviously larger than the change of the excess pore water pressure around the pile of the PTC-400 (60) pipe pile. When the pile driving distance is less than 5m, the pressure of excess pore water changes more obviously. When the pile driving distance exceeds 5m, the pressure of excess pore water gradually decreases and tends to average velocity.